The present invention is directed to safety syringes, and particularly syringes with retractable needles configured to retract after use and prevent re-use and unintended sticking. Retractable syringes are known in the art, which typically include a needle configured to automatically retract into a syringe barrel after delivery of a medicant into a patient. In some designs, a needle stem including a separable or breakable retaining ring thereabout is installed through a barrel proximal end and secured in the barrel distal end. The needle stem may be fixedly secured or selectively secured to a needle. Conventional mechanisms that prevent or inhibit retracting the plunger after retraction of the needle into the syringe barrel have relative advantages and disadvantages, including complexity and cost.
There is desired an improved retractable syringe configured to restrict the plunger from being withdrawn from the syringe barrel after use and retraction of the needle assembly.